<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    let arr = [3,4,9,2,5,6]
    let res = arr.filter(item =>{
      // console.log(item); item数组的每一项
      // return '条件'
      return item > 4
    })
    console.log(res); //res是一个新数组，包含所有符合条件的元素
  </script>
  
</body>
</html>